Fluid-attenuated Inversion Recovery Technique Research Articles

Software for brain tumor diagnosis on magnetic resonance imaging

BACKGROUND: The main reason for the development and implementation of artificial intelligence (AI) technologies in neuro-oncology is the high prevalence of brain tumors reaching up to 200 cases per 100,000 population. The incidence of a primary focus in the brain is 5%10%; however, 60%70% of those who die from malignant neoplasms have metastases in the brain. Magnetic resonance imaging (MRI) is the most common method for primary non-invasive diagnosis of brain tumors and monitoring disease progression. One of the challenges is the classification of tumor types and determination of clinical parameters (size and volume) for the conduct, diagnosis, and treatment procedures, including surgery.
 AIM: To develope a software module for the differential diagnosis of brain neoplasms on MRI images.
 METHODS: The software module is based on the developed Siberian Brain Tumor Dataset (SBT), which contains information on over 1000 neurosurgical patients with fully verified (histologically and immunohistochemically) postoperative diagnoses. The data for research and development was presented by the Federal Neurosurgical Center (Novosibirsk). The module uses two- and three-dimensional computer vision models with pre-processed MRI sequence data included in the following packages: pre-contrast T1-weighted image (WI), post-contrast T1-WI, T2-WI, and T2-WI with fluid-attenuated inversion-recovery technique. The models allow to detect and recognize with high accuracy 4 types of neoplasms, such as meningioma, neurinoma, glioblastoma, and astrocytoma, and segment and distinguish components and sizes: ET (tumor core absorbing Gd-containing contrast), TC (tumor core) = ET + Necr (necrosis) + NenTu, and WT (whole tumor) = TC + Ed (peritumoral edema).
 RESULTS: The developed software module shows high segmentation results on SBT by Dice metric for ET 0.846, TC 0.867, WT 0.9174, Sens 0.881, and Spec 1.000 areas. The testing and validation were done at the international BraTS Challenge 2021 competition. The test dataset yielded DiceET 0.86588, DiceTC 0.86932, and DiceWT 0.921 values, placing the developed software module in the top ten. According to the classification, the results demonstrate high accuracy rates of up to 92% in patient analysis (up to 89% in slice analysis), a very high potential, and a perspective for future research in this area.
 CONCLUSIONS: The developed software module may be used for training specialists and in clinical diagnostics.

Technical note: A spiral fluid-attenuated inversion recovery magnetic resonance imaging technique for stereotactic radiosurgery treatment planning for trigeminal neuralgia.

Magnetic resonance imaging (MRI) is commonly used in treatment planning for stereotactic radiosurgery (SRS) of trigeminal neuralgia (TN). With current MRI techniques, the delineation of the trigeminal nerve root entry zone (REZ) may be degraded due to poor contrast and artifacts. The purpose of this work is to develop an MRI technique with better delineation of the trigeminal nerve REZ to improve SRS treatment planning for TN. A spiral fluid-attenuated inversion recovery (FLAIR) MRI technique was developed to improve image quality by improving tissue contrast, fluid suppression, artifact reduction, and signal-to-noise ratio (SNR). A concomitant-phase compensation method based on spiral gradient waveforms was implemented to minimize artifacts due to magnetic field change induced by the metal frame used in Gamma Knife treatment planning. The image quality of spiral FLAIR was assessed in four healthy volunteers. The geometric accuracy was quantitatively evaluated by registering spiral FLAIR to computed tomography (CT) images and comparing it with existing MRI techniques. The spiral FLAIR technique demonstrated better delineation of the trigeminal nerve REZ, improved tissue contrast of the brain stem, and minimized flow artifacts, compared to steady-state free precession (SSFP) MRI. Spiral FLAIR also improved fluid suppression, SNR, and artifacts, which contributed to better delineation of the trigeminal nerve REZ compared to conventional Cartesian FLAIR. The measured mean (± standard deviation) distance between spiral FLAIR and CT images is 0.98 ± 0.56mm, comparable to 0.40 ± 0.26mm in 3T T1 spoiled gradient echo (T1-SPGR), 0.59 ± 0.25mm in 3T SSFP, 0.66 ± 0.38mm in 1.5T T1-SPGR, and 0.61 ± 0.25mm in 1.5T Cartesian FLAIR. A spiral FLAIR technique with improved image quality and good geometric accuracy provides a potential alternative for treatment planning in SRS for TN patients.

Improving the image quality of 3D FLAIR with a spiral MRI technique.

Fluid-attenuated inversion recovery (FLAIR) nulls the CSF signal and is widely used in neuro MRI exams. A 3D scan can provide high SNR, contiguous coverage, and reduced sensitivity to through-plane CSF flow. In this work, a 3D spiral FLAIR technique is proposed to improve the image quality of conventional 3D Cartesian FLAIR. The 3D spiral FLAIR sequence incorporated a spiral-in/out readout to preserve higher scan efficiency and eliminate off resonance-induced artifacts observed with a commonly implemented spiral-out readout, a compensation approach to minimize phase errors due to the concomitant fields accompanying the spiral gradient, and an adapted variable flip angle scheme to preserve scan efficiency and maintain a long and stable echo train. 3D Cartesian and spiral FLAIR (~6 min each) were acquired on a 3 Tesla scanner from 6 subjects (age range: 31-64 years; mean: 39.5). Two neuroradiologists rated the images in a blinded fashion on a 5-point scale. The noise performance was assessed quantitatively. Compared to 3D Cartesian FLAIR, 3D spiral FLAIR exhibits greater reduction of artifacts from CSF, especially anterior to the brain stem (rated better in 4 cases), artifacts attributed to blood/flow in the deep brain (better or much better in all 6 cases), and superior overall image quality (much better in 5 cases) despite residual susceptibility artifacts near the nasal cavity. Quantitative assessment demonstrates ~1.5× higher average SNR than Cartesian data. 3D spiral FLAIR achieves higher SNR, reduced CSF, and blood/flow artifacts, providing an alternative to 3D Cartesian FLAIR for neurological exams.

Intracranial hypotension and PRES: a reply

We thank Dr Hong-Liang Zhang and colleagues for their interest and comments on our article [1] about the probable causal association between intracranial hypotension (IH) and posterior reversible encephalopathy syndrome (PRES). We surely agree that further investigations are required in order to better clarify the relationship between these two entities. We are aware that the association between IH and PRES has not been reported in literature, that we should be cautious about proposing this diagnosis and that this physiopathological correlation is only a presumption. Our hypothesis is supported by the prompt resolution of the neurological symptoms and radiological alterations of both IH and PRES only after the treatment of IH with a blood patch without any other specific therapy used to treat PRES and any other clear cause of PRES. Some of the possible etiologies of PRES were ruled out with clinical examination and laboratory data. They were negative for arterial hypertension, proteinuria, liver function abnormalities, peripheral edema on examination; moreover, none of the drugs used in the peripartum period could be responsible for PRES. About the diagnosis of IH, although lumbar puncture is the gold standard, we considered it dangerous because of the accentuated venous hypertension and consequent brainstem descent. Moreover, imaging revealed not only the presence of pachimeningeal thickening, enhancing after contrast administration, but also, as mentioned, downward displacement of brain and engorgement of venous structures, such as dural sinuses, Galen vein and epidural venous plexi associated with bilateral subdural cerebrospinal fluid collections, signs suggestive of IH. It is correct to note that the Fig. 1a in our article is a T2-weighted image acquired with a fluid attenuated inversion recovery technique. Even considering the limitations of our single experience and of the proofs provided, we look forward with a great interest to other reports that could eventually clarifying the relationship between IH and PRES.

Three-Dimensional Fluid Attenuated Inversion Recovery Imaging With Isotropic Resolution and Nonselective Adiabatic Inversion Provides Improved Three-Dimensional Visualization and Cerebrospinal Fluid Suppression Compared to Two-Dimensional Flair at 3 Tesla

In this investigation, we compare two-dimensional (2D) fluid-attenuated inversion recovery (FLAIR) imaging of the brain to an isotropic three-dimensional (3D) FLAIR technique that uses a modulated refocusing flip angle echo train and parallel imaging with 2D acceleration. Two-dimensional and 3D FLAIR sequences were obtained in 16 patients. All examinations were performed on a 3 Tesla (T) magnetic resonance (MR) system. Flow artifacts within the subarachnoid space and ventricles were scored using a 4-point scale. For 2D and 3D FLAIR, the signal-to-noise ratios and contrast-to-noise ratios were calculated. Compared to 2D FLAIR, the 3D FLAIR images were less degraded by flow artifacts in the subarachnoid space and ventricle (P < 0.03) based on the qualitative imaging scores. Signal-to-noise ratios and contrast-to-noise ratios were higher for 3D FLAIR (P < 0.02) for all variables when compared with 2D FLAIR sequence. The acquisition time for whole brain isotropic fast spin echo 3D FLAIR can be dramatically reduced by using an extended echo train with flip angle modulation and parallel imaging. The adiabatic, nonselective inversion pulse encompasses the entire volume and provides uniform suppression of the cerebrospinal fluid signal eliminating cerebrospinal fluid pulsation artifacts. Other advantages include reformatting in any desired plane, volume measurements, displays of surface anatomy, and coregistration.

Echo-planar FLAIR imaging in evaluation of intracranial lesions.

Fluid-attenuated inversion-recovery (FLAIR) imaging is a magnetic resonance imaging technique that improves lesion detection in the brain. This technique suppresses signal from free water in cerebrospinal fluid and maintains the hyperintense lesion contrast of T2-weighted spin-echo imaging. Unfortunately, conventional FLAIR imaging requires a long acquisition time and provides a limited number of sections. A combination of echo-planar imaging and FLAIR imaging offers the image contrast effects of FLAIR imaging and the speed of echo-planar imaging. Clinically, the echo-planar FLAIR technique is most helpful in detecting subtle, early lesions that do not enhance, such as early infarct, demyelinating disease, early infection, and trauma. The increased magnetic susceptibility effect associated with the echo-planar technique can be clinically useful in detecting subtle hemorrhage and cavernous angioma. Echo-planar FLAIR imaging is a practical and efficient means of screening the entire brain in a short time.

CSF-suppressed T2-weighted three-dimensional MP-RAGE MR imaging.

Fluid-attenuated inversion recovery (FLAIR) is a pulse sequence used for acquiring T2-weighted images of the brain and spine in which the normally high signal intensity of CSF is greatly attenuated. The CSF-suppressed T2-weighted contrast of this technique may be more sensitive to a variety of disorders than that of conventional T2-weighted imaging. The primary disadvantage associated with conventional spin-echo implementations of FLAIR is the relatively limited anatomic coverage that can be achieved in a reasonable imaging time. We developed and optimized a three-dimensional magnetization-prepared rapid gradient-echo (3D MP-RAGE) pulse sequence that combines CSF-suppressed T2-weighted contrast similar to existing FLAIR techniques with anatomic coverage characteristic of 3D imaging. A preliminary evaluation of the new sequence was performed by imaging healthy volunteers and patients with multiple sclerosis.